bonsoir a/ -4/49*35/12=-140/588=-70/294=-35/147=-5/21
-5/3+-5/21=-35-5/21=-40/21
b/1/4-1/5=5-4/20=1/20
7+37/9=63+37/9=100/9
100/9*1/20=100/80=50/90=25/45=5/9
c/ 2/5*15/8=30/40=3/4
1/3-3/4=9-4/12=5/12
5/12+7/12=12/12=1
1/5-7/2=35-2/10=33/10
1:33/10=1*10/33=10/33